Salem

Not sure if intended?
built sevral smelters, (10 to be precise)
sometimes i put in lime before ores just because i might have forgotten to refill crushers and have to wait for them as im to lazy to chip ore boulders.
using 12ish lime and 13ish ores or 10 ish lime, one certain smelter sometimes ends with no dross,no iron,nothing,just empty.
It only happens random and mabybe once in 10 runs or so.
Reproduced it a few times by adding lime before ores and only on a certain smelter and that makes me confused.

If you burn lime without ore - you will get same result. I think you just forget to fill smelter with ore before you lit it. You have many smelters - easy way to make a mistake.

that is true, I've built dozens of smelter since closed beta and I have never had this unexpected result unless I filled it with nothing or just lime

I did think of that for the first and second time.
then i double,tripple checked and after a while i got the same result, its only if u put the lime first and then ore but ore was there 100%
im not talking about like once here.
20 test runs when doublechecking so ore and lime was in the smelter had a result of twice

Maybe we need more exact details. I have a routine and I always put the lime in first. I have never had this happen to me. Maybe, purity of ore, the numbers you use. The exact order of lime, fuel, ore. If it is one particular smelter, what is special about that smelter? Keep trying to reduplicate it and find out the exact details of what you are doing when it happens.